There are a number of open-source command line tolls available for Unix that measure memory-to-memory network throughput. Some of the more popular tools include:

Each of these tools has slightly different features, and slightly different architectures, so you should not expect any one tool to have everything you need. It is best to be familiar with multiple tools, and use the right tool for your particular use case.

One key difference is whether or not the tool is single-threaded or multi-threaded. If you want to test parallel stream performance, you should use a multi-threaded tool such as iperf2.

Tool feature comparison
Feature iperf 2.0.13+ iperf 3.7+ nuttcp 8.x
multi-threading -P    
JSON output   –json  
CSV output -y    
FQ-based pacing –fq-rate –fq-rate  
multicast support –ttl   -m
bi-directional testing –dualtest –bidir  
retransmit and CWND report
on by default
skip TCP slow start   –omit  
set TCP congestion control alg. -Z –congestion  
zero-copy (sendfile)   –zerocopy  
UDP burst mode     -Ri#/#
Select CPU core   -A -xc#/#
MS Windows support yes no no

Based on experience, recommend the following:

  • Use iperf2 for parallel streams, bidirectional, or MS Windows-based tests
  • Use nuttcp for high-speed UDP testing
  • Use iperf3 otherwise. In particular if you want detalied JSON output

For all 3 tools we recommend running the latest version, as all tools have been getting important updates every few months. In particular, there are known UDP issues with iperf 2.0.5 and iperf 3.1.4 or earlier, and these versions should be avoided for UDP testing